Motion — Quick Revision
An object is in motion when its position changes with time. Distance is the total path length covered (a scalar); displacement is the shortest straight-line distance from the start to the end point, with direction (a vector). Speed is distance per unit time; velocity is displacement per unit time. Acceleration is the rate of change of velocity. For uniform acceleration, the three equations of motion relate initial velocity u, final velocity v, acceleration a, time t and distance s. Motion is shown using distance–time and velocity–time graphs — the slope of a velocity–time graph gives acceleration.
Key Points
- •Distance = total path (scalar); Displacement = shortest path (vector)
- •Speed = distance/time; Velocity = displacement/time
- •Acceleration a = (v − u)/t
- •v = u + at
- •s = ut + ½at²
- •v² = u² + 2as
- •Slope of velocity–time graph = acceleration